Abstract

The energy-sensitive detection of heavy ions with calorimetric low temperature detectors was investigated in the energy range of , commonly used for accelerator mass spectrometry (AMS). The detectors used consist of sapphire absorbers and superconducting aluminum transition edge thermometers operated at . They were irradiated with various ion beams provided by the VERA tandem accelerator in Vienna, Austria. The relative energy resolution obtained was , even for the heaviest ions such as . In addition, no evidence for a pulse height defect was observed. This performance allowed for the first time to apply a calorimetric low temperature detector in an AMS experiment. The aim was to precisely determine the isotope ratio of for several samples of natural uranium, being known as a sensitive monitor for neutron fluxes. Replacing a conventionally used detection system at VERA by the calorimetric detector enabled to substantially reduce background from neighboring isotopes and to increase the detection efficiency. Due to the high sensitivity achieved, a value of could be obtained, representing the smallest ratio measured at the time. In addition, we contributed to establishing an improved material standard of , which can be used as a reference for future AMS measurements.